Collar locator

ABSTRACT

A collar locator for use in a tool string for locating casing collars downhole in a borehole. The collar locator employs radially spaced apart outwardly biased projections which releasably engage the annulus formed between the collar and spaced adjacent joints of the casing with a releasable action depending upon the spring tension and the geometrical configuration of the projection. A weight indicator affixed to the upper end of the tubing string indicates engagement of the collar locator with a casing collar.

United States Patent Watson Sept. 2, 1975 COLLAR LOCATOR [76] Inventor: Billy Ray Watson, Box 756, Pnmary Exammerjferry Myracle Monahans 79756 Attorney, Agent, or FzrmMarcus L. Bates [22] Filed: May 28, 1974 [57] ABSTRACT PP 473,486 A collar locator for use in a tool string for locating casing collars downhole in a borehole. The collar loca- 52 us. c1 73/151- 166/64 P Y radially Spaced apart ("Hardly biased 51 Int. Cl. Ezib 47/00 Pmiections which releasably engage the annulus 5 Field of Search N 73 151 152. 1 4 1 13 formed between the C0113! and spaced adjacent joints 6 5 of the casing with a releasable action depending upon the spring tension and the geometrical configuration [56] References Cited of the projection. A weight indicator affixed to the upper end of the tubing string indicates engagement of UNITED STATES PATENTS the collar locator with a casing collar. 3,381,750 5/1968 Brown 166/64 3,474,539 10/1969 Moore 73/151 x 6 Clams, 4 Drawmg Flgures COLLAR LOCATOR BACKGROUND OF THE INVENTION Many borehole operations require that an apparatus be positioned at a precise downhole location. Boreholes are cased or lined with a metal pipe using collars to connect together the joints of the casing, thereby forming a string of casing. The string of casing is electronically studied following it installation with the individual collars being precisely located respective to borehole depth and the resulting data stored or logged, so that anyone can subsequently consult the logs to ascertain the collar closest adjacent to a particular desired elevation of the borehole. Hence, by moving a few feet up or downhole with respect to an identified collar, the accuracy of locating any desired elevation in the borehole is greatly increased.

For this reason it is desirable to have inexpensive, reliable, compact, and simple apparatus made available for locating casing collars downhole in a borehole.

SUMMARY OF THE INVENTION This invention comprehends downhole equipment, and specifically, a collar locator apparatus comprising a main body having an axial passageway formed therethrough and threaded connectors at each extremity thereof for connection into a tubing string so that the locator can be run downhole as part of a tool string.

A plurality of spring loaded radially spaced apart tagging elements are received in captured relationship within the main body and have abutments depending therefrom which releasably engage a shoulder formed by adjacent casing joints where the joints are joined together by the casing collar. A weight indicator is utilized to sense each time a collar is tagged.

Accordingly, a primary object of the present invention is the provision of improvements in collar locator apparatus for locating collars which join together joints of tubular goods.

Another object of the invention is to provide a collar locator apparatus which sequentially and repeatedly tags any number of adjacent collars.

A further object of this invention is to disclose and provide improvements in well bore apparatus which enables a weight indicator to be utilized in conjunction with a collar locator device for exactly locating various collars downhole in a borehole.

A still further object of this invention is to provide a device which can be series connected into a tubing string and which releasably engages casing collars to thereby ascertain the elevation of a particular collar downhole in a borehole.

These and various other objects and advantages of the invention will become readily apparent to those skilled in the art upon reading the following detailed description and claims and by referring to the accompanying drawings.

The above objects are attained in accordance with the present invention by the provision of a combination of elements which are fabricated in a manner substantially as described in the above abstract and summary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a part diagrammatical, part schematical, fragmentary, part cross-sectional view which discloses a collar locator apparatus made in accordance with the present invention being used downhole in a borehole;

FIG. 2 is an enlarged, cross-sectional view of part of the apparatus disclosed in FIG. I, with some parts being broken away therefrom to conserve drawing space; and,

FIGS. 3 and 4, respectively, are cross-sectional views taken along lines 33 and 4-4, respectively, of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 of the drawings, a cased borehole 10 has apparatus 12 made in accordance with the present inven tion disposed downhole therein. The apparatus includes a tubing string 14 having a collar locator 16 series connected thereinto. A packer 18, or other downhole apparatus, such as a jet perforator gun or an instrument package, is also series connected into the tubing string with the tubing sometimes continuing as illsutrated by numeral 19 in the drawings.

Opposed adjacent joints of casing have the adjacent terminal ends thereof spaced apart from one another to present spaced apart shoulders 20 which cooperate together and with a collar 21 to define an annulus.

Looking now to the details of FIG. 2, together with FIGS. 3 and 4, wherein the collar locator of FIG. 1 is shown in greater detail. A box 22 generally forms the upper end of the collar locator although the apparatus can be run into the hole in the manner of either FIGS.

1 or 2 as may be deemed desirable. Faces 24 and 26 define opposed terminal ends of the apparatus while numeral 28 broadly indicates an axially disposed longitudinally extending flow passageway formed through the apparatus so as to flow communicate the separated portions of the tubing string with one another. The inside peripheral wall surface of the passageway is generally indicated by the numeral 30.

The pin end 33 and box end 34 are threaded in the usual manner. Sloped circumferentially extending shoulder 36 defines the major and minor diameters of the main body of the tool. The cylindrically and vertically depending wall at 38 forms a skirt having a terminal edge portion 39. Radially spaced apart elongated longitudinally extending undercuts, each having a marginal end portion generally indicated by numeral 40, are positioned parallel to the axial center line of flow passageway 28. Numeral 40 is placed near the lower extremity of the undercut while numeral 42 indicates the remaining marginal extremity of the undercut.

A tagging element 43 is slidably received in close tolerance relationship for radial movement within each of the elongated slots and is comprised of a substantially flat surface 44 which inwardly slopes toward a marginal end portion 46 which has been reduced in cross-section and formed into a tongue. The tongue is loosely captured within the marginal end portion 42 of the slot.

The outermost radially disposed collar engaging portion 48 of the tagging element inwardly slopes at spaced surfaces 50 and 52 toward each of the opposed tongues 46 and 54. The surface 50 preferably is disposed 30 relative to a casing wall, or 150 relative to vertical surface 44, while the sloped surface 52 is disposed relative to an interior peripheral wall surface of a casing, or relative to the vertical wall surface 44.

Tongue 54 is formed in opposition to tongue 46 and defines the remaining marginal end portion of the tagging element. Each of the tongues are loosely received in each of the cavities and 42 so that the outwardly directed enlargement 48 can move the entire tagging element radially inwardly toward the axial center line of the main body of the apparatus.

Counterbores 55, 56 and 57 are formed on the interior wall of the tagging element in spaced apart relationship respective to one another and receive a compression spring 58 therewithin with the springs preferably jointly exerting an outwardly directed force of -150 pounds.

The before mentioned cavity within which tongue 54 is received preferably comprises a nut 60 which threadedly engages the main body at 62 to that the circumferentially extending skirt member 64 captures tongue 54 therewithin.

Numerals 66 and 68 indicate that the preferred form of the invention utilizes four radially spaced apart slots within which a tagging element is recieved.

As seen in FIG. 1, a weight indicator 70 is attached to the upper extremity of the tubing string in the usual manner so that the apparent weight of the entire tubing string can be monitored.

In fabricating the apparatus of the present invention. the upper skirt member 39 preferably is formed by turning an annulus into the extreme marginal end of the slot at 42. The opposed end of the slot is milled so that end portion 40 of the slot does not communicate with the similar end portions of the remaining radially spaced apart slots.

The before mentioned circumferentially extending skirt member 64 provides an annulus within which the tongue portion 54 of the tagging element is received so that each of the tagging elements may be placed with the tongue 46 thereof received under the skirt member 39, the spaced compression springs are then assembled in the illustrated manner of FIG. 2, after which all four of the tagging elements are forced into the ratracted configuration by utilizing clamps together with a vice, or the like. The nut 60 is then screwed into position so that each of the tagging elements are captured within their respective slots.

The apparatus preferably is utilized in conjunction with workover apparatus having means for running tubing into and out of a cased borehole, and further having weight indicating means for weighing the tubing string. The collar locator of the present invention is connected with the box end 22 looking up in the illustrated manner of FIG. 1, although the tool could equally well be run into the hole with the box end looking down in the manner of FIG. 2, and such an expedient is sometimes desirable.

With the collar locator being series connected in the tubing string, it is now in condition to be run downhole in conjunction with other equipment 18 so that. the various casing collars can be tagged by engaging the tagging elements with the annular shoulder formed by the makeup in the collar between adjacent casing joints.

The main body of the collar locator is of a crosssectional area which equals or exceeds the tensil strength of the remainder of the tubing string. The axial passageway formed through the main body provides a flow path from the upper extremity of the tubing 14 to the tailpipe 19. The threaded connectors enable each extremity of the main body to be connected into the tubing string.

The plurality of radially spaced apart longitudinally disposed slots are formed within the outer marginal portion of the main body and are provided with the before mentioned skirt members at each extremity thereof which form anchor means so that the opposed end portions of the tagging elements are received in captured relationship within opposed end portions of the slot. Hence, the circumferentially extending annulus formed by the inwardly directed opposed skirt members form anchors for loosely capturing the opposed tongues of the tagging elements therewithin.

The outwardly directed projection on each of the tagging elements releasably engage the annular shoulder formed by the spaced casing joints which are joined together by the collars. The slope 50, 52 together with the force of compression spring 56 determines the change in the reading of the weight indicator each time the tagging element encounters the annulus formed between the spaced ends of adjacent casing joints. It is preferred that the slope be of a value to cause one to three thousand pounds change in the weight indicator each time the projection engages the collar.

I claim:

1. In a well bore workover apparatus having means for running tubing into and out of a cased borehole, and further having weight indicator means for weighin g the tubing string, the combination comprising a collar locator series connected in the tubing string for tagging collars by engaging the makeup formed in the collar between adjacent casing joints;

said collar locator comprising a main body having an axial passageway formed therethrough and threaded connectors at each extremity thereof for connection into the tubing string;

a plurality of radially spaced apart longitudinally disposed slots formed wtihin an outer marginal portion of said main body;

anchor means formed at each marginal end portion of said slot; a plurality of tagging elements, each tagging element having opposed end portions which are received in captured relationship within opposed end portions of said slot by'said anchor means;

means biasing each tagging element radially outwardly of said main body, and means forming an outwardly directed projection on each said tagging element for releasably engaging the annular shoulder formed by spaced casing joints joined together by a collar.

-2. The collar locator of claim I wherein each tagging element has opposed end portions formed into a tongue;

said anchor means being a cavity formed at each marginal end of said slot;

one cavity being in the form of a skirt member which is removably affixed to said main body and position with said skirt being placed in overlying relationship respective to said slot to thereby enable assembly of the components of the collar locator.

3. The collar locator apparatus of claim 1 wherein said outwardly directed projection on each tagging element includes a casing contacting portion which slopes in opposed directions toward said main body.

4. The collar locator of claim 3 wherein said sloped surface forms an angle of 15 to respective to the axial center line of the passageway.

6 5. The collar locator of claim 1 wherein said biasing one sloped surface forming an angle of 60 and the means is a compressed Spring located between Said remaining sloped surface forming an angle of 30 main body and said tagging element.

6. The collar locator of claim 1 wherein said outwardly directed projection on each tagging element includes a casing contacting portion which slopes in opagainst Said tagging element posed directions toward said main body;

with respect to the axial passageway; and, said biasing means exerting a force of 80 pounds 

1. In a well bore workover apparatus having means for running tubing into and out of a cased borehole, aNd further having weight indicator means for weighing the tubing string, the combination comprising a collar locator series connected in the tubing string for tagging collars by engaging the makeup formed in the collar between adjacent casing joints; said collar locator comprising a main body having an axial passageway formed therethrough and threaded connectors at each extremity thereof for connection into the tubing string; a plurality of radially spaced apart longitudinally disposed slots formed wtihin an outer marginal portion of said main body; anchor means formed at each marginal end portion of said slot; a plurality of tagging elements, each tagging element having opposed end portions which are received in captured relationship within opposed end portions of said slot by said anchor means; means biasing each tagging element radially outwardly of said main body, and means forming an outwardly directed projection on each said tagging element for releasably engaging the annular shoulder formed by spaced casing joints joined together by a collar.
 2. The collar locator of claim 1 wherein each tagging element has opposed end portions formed into a tongue; said anchor means being a cavity formed at each marginal end of said slot; one cavity being in the form of a skirt member which is removably affixed to said main body and position with said skirt being placed in overlying relationship respective to said slot to thereby enable assembly of the components of the collar locator.
 3. The collar locator apparatus of claim 1 wherein said outwardly directed projection on each tagging element includes a casing contacting portion which slopes in opposed directions toward said main body.
 4. The collar locator of claim 3 wherein said sloped surface forms an angle of 15* to 75* respective to the axial center line of the passageway.
 5. The collar locator of claim 1 wherein said biasing means is a compressed spring located between said main body and said tagging element.
 6. The collar locator of claim 1 wherein said outwardly directed projection on each tagging element includes a casing contacting portion which slopes in opposed directions toward said main body; one sloped surface forming an angle of 60* and the remaining sloped surface forming an angle of 30* with respect to the axial passageway; and, said biasing means exerting a force of 80 pounds against said tagging element. 